From A to ZZZZZZZ: Is Cannabis a Sleep Remedy?

It’s no secret that many American adults struggle with getting a good night’s sleep. Between 50 and 70 million adults have a sleep disorder,1 with insomnia being one of the most common. Roughly 10% of American adults experience chronic insomnia.2

Anecdotally, cannabis is often hailed as a potential sleep remedy, and Americans are embracing it enthusiastically: One survey of retail cannabis users in Colorado found that 74% of respondents reported using cannabis to help them sleep.3

But does it actually work?

The short answer: It’s complicated. The research on cannabis and sleep is still “minimal,” according to Bhanuprakash Kolla, MD, an associate professor of psychiatry at the Mayo Graduate School of Medicine in Rochester, Minnesota. However, it’s clear that various cannabis products—whole-plant cannabis, cannabis-derived sprays, and isolated cannabinoids such as THC or CBD—all have differing effects on sleep. According to Kolla, it’s necessary to “draw the distinction as to what cannabinoid we are dealing with.” Some products have been shown to have positive effects on sleep under certain circumstances, but the effects can change over time, and cannabis products can have a negative influence on sleep in other conditions. Researchers are thus still teasing out which specific products (or which cannabinoids) have legitimate sleep benefits and under what circumstances.

Role of the Endocannabinoid System in Sleep
The endocannabinoid system is known to help regulate the sleep/wake cycle. In mammals, the primary circadian clock is located within the hypothalamus in a group of cells called the suprachiasmatic nucleus (SCN). Cannabinoid receptors are widespread in the hypothalamus and throughout the brain, and there are multiple mechanisms by which cannabinoids that act on these receptors could alter the functioning of the SCN—either by altering inputs into the SCN or by interacting with outputs from the SCN.4

There’s extensive evidence of a link between the endocannabinoid system and sleep. The levels of various endocannabinoids fluctuate during the sleep/wake cycle, and particular endocannabinoids are known to promote specific types of sleep (either rapid eye movement [REM] sleep or non-REM sleep) through varying mechanisms and brain structures.5 The relationship between sleep and the functioning of the endocannabinoid system appears to be bidirectional in that endocannabinoids promote specific types of sleep but abnormal sleep can cause dysregulation in the endocannabinoid system.4

Interestingly, the endocannabinoid system may facilitate normalization of sleep patterns after disruption. Animal studies have demonstrated that there’s a significant increase in cannabinoid receptor density during the rebound period after sleep deprivation, which suggests that the endocannabinoid system could be helping to return sleep patterns to normal.6

Cannabis and Isolated THC: Acute Influences on Sleep
In surveys, cannabis users frequently report that cannabis improves their sleep.3,7,8 One survey found that this was true even for participants for whom sleep wasn’t their primary reason for using cannabis.7 Studies of THC that have relied on objective measurements of sleep have often supported these subjective reports, showing that administration of THC decreases both sleep onset latency—that is, the amount of time it takes an individual to fall asleep—as well as time spent awake during the night.9-12

Cannabis use also influences the organization of sleep—that is, the amount of time spent in each stage of sleep. The research on these effects goes back to the 1970s, when multiple animal studies in several different species demonstrated that short-term administration of THC causes a decrease in REM sleep as well as an increase in slow wave sleep (SWS).4 Short-term administration of THC and short-term inhalation of whole-plant cannabis have been shown to have similar effects in several human studies as well.12,13-15 Although these positive findings haven’t been replicated in all studies, the trend in the research is that cannabis has a beneficial effect on sleep in the short term.11,16,17

THC and Inhaled Cannabis: Chronic Effects on Sleep
Unfortunately, repeated studies indicate that these sleep benefits decrease over time. Numerous studies—some relying on subjective self-report and others relying on objective measurements from polysomnography—have found that users develop a tolerance to cannabis with extended use. Cannabis appears to lose some of its sleep-inducing effects after this, and some research suggests that sleep efficiency may worsen as well.8

The effects of cannabis on sleep architecture also change over time. While THC and whole-plant cannabis generally cause a decrease in REM sleep and an increase SWS in the short term, multiple animal models and human studies have found that chronic usage results in a decrease in SWS over the longer term, along with an inconsistent effect on REM sleep.4,15,18 In one small placebo-controlled study, participants who smoked cannabis daily for 10 days showed increases in SWS for first four days, but had a steady decline in SWS after that. By the eighth day, SWS was significantly lower than baseline and it remained depressed even in the week after participants stopped using cannabis.15

The negative sleep effects of cannabis generally and THC in particular are most obvious when individuals try to discontinue use.8 “Sleep disruption is a very common symptom of withdrawal,” Kolla says, noting that it occurs in about two-thirds of users who try to quit. “You’re sleeping poorly, it’s harder to get to sleep, and you’re sleeping for shorter amounts of time.”

Research using polysomnography demonstrates that individuals who stop using cannabis experience an increase in sleep onset latency and in time spent awake during the night, along with a reduction in total sleep time and in sleep efficiency.8 Sleep difficulties often cease within a couple of weeks after discontinuation of cannabis use, but several studies have found that the disturbances persist for a much longer period—as long as 45 days.19,20 Such difficulties are more significant among heavier users, but they’re common even among individuals who had been receiving comparatively low doses of oral THC.21

Sleep problems are often a major factor contributing to relapse among individuals who try to quit using cannabis.8,22 In one survey, 65% of cannabis users who attempted to quit reported problems with sleep as the primary reason for why they relapsed.23

CBD and Sleep
“Research on CBD is relatively nascent. CBD as an individual chemical entity has not been widely available until very, very recently,” says Ryan Vandrey, PhD, an associate professor of psychiatry and behavioral sciences at Johns Hopkins School of Medicine. Accordingly, “we know a lot less about the effects CBD has on sleep.”

Some research in animals suggests a positive impact. In a rat model, CBD prevented anxiety-induced suppression of REM sleep—but it’s worth noting that CBD likely induced this effect on REM sleep via its anxiolytic effect rather than through a sleep-regulation mechanism.24 Other research suggests that the effects of CBD could vary depending on dosage. In one study of rats, higher doses increased REM sleep latency on the day of administration, whereas midrange-dose CBD decreased REM sleep latency the day after administration, as compared with placebo.25

With respect to its impact on the sleep-wake cycle, a number of studies suggest that CBD has differing effects depending on dose. At lower doses, CBD appears to promote alertness in both animals and humans.26 In a double-blind, placebo-controlled crossover study of young adults, for instance, a 15-mg dose of CBD counteracted residual sedative effects of THC and increased wakefulness.11 This last study is consistent with other studies suggesting that CBD counteracts some of the negative effects of THC (sleep and otherwise).27 At higher doses, CBD has been shown in rats and in humans to have a sedating effect, increasing total sleep time and decreasing the frequency of nighttime arousals.25,27,28

Importantly, not all studies of CBD have confirmed these patterns regarding high-dose CBD. In a recent randomized, double-blind, placebo-controlled crossover study of 27 healthy volunteers, a single high dose (300 mg) of CBD had no statistically significant impact on multiple measures of sleep, including total sleep time, sleep onset latency, wake time during the night, or the percentage of time that participants spent in each stage of sleep.29 Furthermore, a 2019 study of CBD in an outpatient psychiatric population of participants with a primary complaint of either sleep or anxiety found that CBD improved sleep in the first month of use, but these improvements weren’t sustained over the final two months of the three-month study.30

According to Vandrey, several of the clinical trials that have found a sedative effect of CBD have been trials in which participants were taking other medications. “CBD has been shown to affect the metabolism of other drugs,” Vandrey says. “So the sedation that was observed in clinical trials of CBD most likely is a result of drug-drug interaction with other sedating medications.”

Cannabis and Sleep in Patients With Chronic Pain
Regardless of how cannabis influences sleep in healthy individuals, there’s interest in determining whether it might be useful for improving sleep in individuals with certain conditions, such as chronic pain. Chronic pain affects up to 20% of adults in developed countries, and pain, in turn, frequently interferes with the ability to sleep. Thus, a number of studies have investigated the effects of various cannabis products in the context of pain.

The majority of studies in patients with chronic pain looking at cannabis and sleep have used nabiximols, a cannabis-based spray containing a 1:1 ratio of THC and CBD. These studies have generally found a positive effect on sleep. A recent review article on cannabis and sleep identified five clinical studies on nabiximols that had looked at sleep as a treatment outcome in individuals with chronic pain; all five reported subjective improvements in sleep quality and/or sleep disturbances.31 As a caveat, the improvements observed in sleep in these studies may have been because of the impact of cannabinoids on pain, not because they are working through a sleep-regulation mechanism.

Studies of THC for improvement of sleep in patients with pain have been mixed, but again, most have shown that THC has a positive impact on sleep. Several studies of patients with differing types of chronic pain have examined nabilone (a synthetic form of THC) either as an adjuvant or alternative to other drugs used to reduce pain and improve sleep, and most of those studies have reported that nabilone has a positive impact on sleep.32-35 But the evidence isn’t uniform, and a few studies have found that nabilone doesn’t have a significant effect on sleep in patients with pain.36,37

While most research on sleep and chronic pain has examined the effect of either THC or nabiximols, a few studies have looked at whole-plant medical cannabis. These, too, have found that cannabis is linked to improved sleep.38,39 However, one of these studies found that these effects only held for less frequent users, and that frequent use was associated with greater problems with nighttime awakenings and inability to fall asleep in the long term. Based on this finding, the study authors concluded that frequent, longer-term users may develop a tolerance to the sleep-maintaining effects of cannabis and may lose the benefits.39

Cannabis and Sleep in Patients With Obstructive Sleep Apnea
In 2017, Minnesota became the first state in the United States to add obstructive sleep apnea (OSA) to the list of qualifying conditions for receiving medical cannabis. According to Kolla, this decision was based heavily on a single clinical trial focusing on individuals with severe OSA. In this trial, participants were randomized to receive a 2.5-mg daily dose of dronabinol (a synthetic form of THC), a 10-mg daily dose of dronabinol, or placebo. The study found that dronabinol significantly decreased subjective sleepiness over placebo and also produced significant improvements on the apnea-hypopnea index. The study also found that participants receiving higher doses saw more benefit.40 Although these findings are positive, Kolla cautions that the benefits shouldn’t be overstated because the trial demonstrated “statistically significant but not clinically significant improvements in sleep apnea.”

There’s only one other clinical study available on cannabis in individuals with OSA. It found that dronabinol had a positive impact on subjective sleepiness and on apneahypopnea index scores, but while the results were promising, the study was only a proof of concept.41 Accordingly, the American Academy of Sleep Medicine published a position statement in 2018 arguing that there’s not yet sufficient evidence that cannabinoids are efficacious for OSA treatment and that cannabis products should therefore not be used to treat OSA at this point.42

Cannabis and Sleep in Patients With PTSD
Nightmares are a frequent symptom of posttraumatic stress disorder (PTSD), and some initial research has examined whether cannabis (specifically, THC) could improve this symptom. One randomized, placebo-controlled trial of military personnel with PTSD-associated nightmares found that titrated doses of nabilone (0.5 mg to 3 mg) produced a significant reduction in nightmares over seven weeks as compared with placebo.43 Several other studies have likewise shown positive effects of nabilone on PTSD-associated nightmares.44-46 Some of these were open-label trials, however, and one used nabilone as an add-on treatment rather than a stand-alone treatment.

Takeaways for Clinicians
1. The body of literature available on cannabis and sleep is still limited. There is a “pretty sizable literature of good-quality research” on the mechanisms by which cannabinoids could affect sleep, and there are strong data on how cannabis affects sleep under acute circumstances, Vandrey says. But the research on chronic cannabis use and how it relates to sleep function over the long term is still only “modest,” he adds, and the same is true of research on cannabis as a therapy for the treatment of specific sleep disorders.

2. THC has sleep-promoting properties, but it’s not suited for long-term use as a hypnotic. “We know that THC can shorten the time it takes to fall asleep,” Vandrey says. However, with THC, as with all other hypnotic medications, “you don’t want to use it for an extended period of time,” due to the potential for users to develop tolerance to the sleep-promoting effects of the drug and then experience abstinence-induced insomnia when they try to quit. “Common clinical recommendations for any hypnotic medication is not to use it for more than two weeks,” he says.

3. The jury is still out on how CBD affects sleep. It’s a newer product, it’s not as well studied as THC, and the research that exists is somewhat conflicting about its effects.

4. Cannabis products could have value in treating specific sleep disorders in certain populations, but it’s too early to tell. For instance, “CBD in several laboratory studies has been shown to reduce anxiety. So if sleep dysfunction stems from anxiety disorder, there’s a corollary whereby it could make sense that an acute dose of CBD could help initiate sleep in somebody who has an anxiety disorder,” Vandrey says. “But that has not been evaluated in an insomnia population or in a population with the primary diagnosis of an anxiety disorder. So this is extrapolated from other types of data.” He adds, “There have been zero studies of CBD in anyone who has been diagnosed with a sleep disorder.”

Similarly, there’s still insufficient evidence about the impact of cannabis or specific cannabinoids on disorders such as OSA. “There are no well-done studies that show that cannabis or cannabis products significantly clinically improve any of the sleep problems,” Kolla says. He emphasizes the need for additional rigorous research, adding, “Based on the quality of evidence we have right now, I wouldn’t recommend using any cannabis products to treat sleep disorders.”

— Jamie Santa Cruz is a health and medical writer in the greater Denver area.

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